The Palo Alto company led by CEO Wences Casares said that the round was led by Greylock Partners — where Hoffman is a partner — and Index Ventures — where Volpi is a partner. Others involved in the funding include Emergence Capital Partners, PayPal co-founder Max Levchin, Russian investor Yuri Milner and Yahoo co-founder Jerry Yang.

The company raised $20 million in March from Benchmark, Fortress Investment Group and Ribbit Capital, so it has raised a total of $40 million now this year. It said it will use the new funds to broaden the use of bitcoin by general users and to better protect the currency on on their servers.

Xapo provides a so-called vault that bitcoin owners can use to make purchases using a branded debit card. It is also a place where institutional investors can store their bitcoins.

"Let us keep in mind that it’s important not to be short-sighted when examining bitcoin," Casares wrote in a blog about the funding."Today, bitcoin is used primarily as a store of value. Soon, it will be a payment mechanism. In the near future it will be a unit of account. We are thankful to be a part of the journey and the ecosystem."

The company said that its debit cards will begin to be shipped to customers in the middle of this month, issued by financial institutions in the U.S. and Europe that it has yet to name.